BrightPhase Energy has cross-bred a skylight with a venetian blind and a lot of solar technology to come up with what could turn out to be a highly efficient energy system for homes or low-slung commercial buildings.

The Photensity (see photo) essentially allows the building owner to exploit the sun in three ways. First, it contains silicon solar cells rated at about an 18 percent efficiency that convert sunlight into electric power. Second, a fluid-filled pipe collects heat from the sun, which can then be used to heat water in the building or run heat-driven cooling systems. A concentrator does double duty by focusing heat for the pipe and light for the solar cells.

Third, because the photovoltaic cells are mounted on separated strips that resemble the slats in venetian blinds, the Photensity also lets light into the building, reducing the need for internal lights.

If you convert the thermal energy (in btus) and the light (measured in lumens) into watts, the entire system produces power for around $1.80 per watt completely installed.

"We are roughly two to three times more energy dense than some of the better PV modules out there," said David Buemi, co-founder and vice president of sales and marketing who added that the company discounts the amount of heat that a customer might use in its calculations.

Granted, that's a best case scenario coming from the marketing guy of the company, but if it's even somewhat close, it rivals the numbers from the best solar makers. First Solar in November said it had managed to drop the price of producing its cadmium telluride solar panels to $1.08 a watt and sources said that the figure has dropped to 75 cents a watt in some of its factories in Malaysia (see First Solar Reaches Grid-Parity Milestone, Says Report).

But that's just the cost of the modules, which only accounts for around one-third of the cost of a solar system completely installed. A $40 million system for Sempra Generation near Boulder City, Nev. – which consists of 168,300 First Solar panels – costs around $3.17 per watt fully installed, according to a recent note from Mark Bachman, an equity analyst at Pacific Crest.

BrightPhase is part of a small, but growing group of companies trying to break into the market by taking a broader view of solar power. Entech Solar, Distributed Solar Power and Millennium Electric devised photovoltaic units that can also capture heat (see All-in-One Solar Panels and Thermal). Entech plans to sell them to industrial users, such as food processing plants or hospitals, with high power and hot water needs.

Cool Energy in Boulder, Colo., meanwhile, has also released a rooftop Stirling Engine that it says can provide 95 percent of its hot water, 60 percent of its electricity.

BrightPhase effectively is trying to take this one step further by adding in light. Harvesting sunlight, however, can be tricky. If a sun passes over a building, the occupants won't run out of power or heat. Nonetheless, they might get angry about the lack of light in their office

In BrightPhase's overall plan, the lights will be hooked into a network and be turned up and down with the requirements of employees and the sun. Besides being free, sunlight is attractive. A grocery chain, that has examined BrightPhase's system, says that natural lighting (as opposed to something like halogen or florescent) can boost retail sales by 20 percent.

Leaving off the lights works, but there's no guarantee that employees or retailers will leave them off. The sensor/control systems for turning up and down lights as the amount of sunlight increases or decreases, meanwhile, still haven't been perfected. A lost hour of worker productivity can equal the amount of energy you might save in a year with a sensor-enabled dimmer bulb, Konstantinos Papamichael, a professor with the California Lighting Technology Center at UC Davis, has estimated. At a trial in a Wal-Mart, the lighting system wouldn't flip the lights on. The problem? A balloon got lodged near a sensor and convinced the network that perpetual daylight reigned in the store.

Sensors can also be thrown off by white table cloths or people wearing black clothes.

The company, which is currently seeking funds, will try to complete four installations this year.